From 5b18b5a737600fd20ba2045f320d5926ebbf341a Mon Sep 17 00:00:00 2001 From: Mikulas Patocka Date: Thu, 6 Dec 2018 11:41:19 -0500 Subject: block: delete part_round_stats and switch to less precise counting We want to convert to per-cpu in_flight counters. The function part_round_stats needs the in_flight counter every jiffy, it would be too costly to sum all the percpu variables every jiffy, so it must be deleted. part_round_stats is used to calculate two counters - time_in_queue and io_ticks. time_in_queue can be calculated without part_round_stats, by adding the duration of the I/O when the I/O ends (the value is almost as exact as the previously calculated value, except that time for in-progress I/Os is not counted). io_ticks can be approximated by increasing the value when I/O is started or ended and the jiffies value has changed. If the I/Os take less than a jiffy, the value is as exact as the previously calculated value. If the I/Os take more than a jiffy, io_ticks can drift behind the previously calculated value. Signed-off-by: Mikulas Patocka Signed-off-by: Mike Snitzer Signed-off-by: Jens Axboe --- block/blk-core.c | 62 ++++---------------------------------------------------- 1 file changed, 4 insertions(+), 58 deletions(-) (limited to 'block/blk-core.c') diff --git a/block/blk-core.c b/block/blk-core.c index 734b768c9d9d..268d2b8e9843 100644 --- a/block/blk-core.c +++ b/block/blk-core.c @@ -584,62 +584,6 @@ struct request *blk_get_request(struct request_queue *q, unsigned int op, } EXPORT_SYMBOL(blk_get_request); -static void part_round_stats_single(struct request_queue *q, - struct hd_struct *part, unsigned long now, - unsigned int inflight) -{ - if (inflight) { - __part_stat_add(part, time_in_queue, - inflight * (now - part->stamp)); - __part_stat_add(part, io_ticks, (now - part->stamp)); - } - part->stamp = now; -} - -/** - * part_round_stats() - Round off the performance stats on a struct disk_stats. - * @q: target block queue - * @part: target partition - * - * The average IO queue length and utilisation statistics are maintained - * by observing the current state of the queue length and the amount of - * time it has been in this state for. - * - * Normally, that accounting is done on IO completion, but that can result - * in more than a second's worth of IO being accounted for within any one - * second, leading to >100% utilisation. To deal with that, we call this - * function to do a round-off before returning the results when reading - * /proc/diskstats. This accounts immediately for all queue usage up to - * the current jiffies and restarts the counters again. - */ -void part_round_stats(struct request_queue *q, struct hd_struct *part) -{ - struct hd_struct *part2 = NULL; - unsigned long now = jiffies; - unsigned int inflight[2]; - int stats = 0; - - if (part->stamp != now) - stats |= 1; - - if (part->partno) { - part2 = &part_to_disk(part)->part0; - if (part2->stamp != now) - stats |= 2; - } - - if (!stats) - return; - - part_in_flight(q, part, inflight); - - if (stats & 2) - part_round_stats_single(q, part2, now, inflight[1]); - if (stats & 1) - part_round_stats_single(q, part, now, inflight[0]); -} -EXPORT_SYMBOL_GPL(part_round_stats); - void blk_put_request(struct request *req) { blk_mq_free_request(req); @@ -1383,9 +1327,10 @@ void blk_account_io_done(struct request *req, u64 now) part_stat_lock(); part = req->part; + update_io_ticks(part, jiffies); part_stat_inc(part, ios[sgrp]); part_stat_add(part, nsecs[sgrp], now - req->start_time_ns); - part_round_stats(req->q, part); + part_stat_add(part, time_in_queue, nsecs_to_jiffies64(now - req->start_time_ns)); part_dec_in_flight(req->q, part, rq_data_dir(req)); hd_struct_put(part); @@ -1420,11 +1365,12 @@ void blk_account_io_start(struct request *rq, bool new_io) part = &rq->rq_disk->part0; hd_struct_get(part); } - part_round_stats(rq->q, part); part_inc_in_flight(rq->q, part, rw); rq->part = part; } + update_io_ticks(part, jiffies); + part_stat_unlock(); } -- cgit v1.2.3